Current status of the Russian National Medical and Dosimetric Registry

The Chernobyl accident and radiation risks: dynamics of epidemiological rates (morbidity, disability and death rates) according to the data in the national registry

V .K. Iv anova

&

A. F. T sybb

In 1986,immediatelyafter the Chernobylaccident, the Ministry of Public Health of the then-USSR adopted a large-scale programme to establish the All-UnionRegistry of persons exposedto radiation. Towards 1992 (by the tim e the USSRcollapsed) the data base of the Registry co mprised med ical and dosimetricinformation for 659292peopl e in- cluding thatfor284 919 em ergen cyworkers (EWs or "liq u ida tors"). All republics of the former USSR as well as'a wide range of scie ntific an d practical institu tio ns wereinvolvedin theestablish- mentof theRegistry(1).

At present, in accordance with the Decree of the Government ofRussia (1948 of 22.09.93 ),the National Radi atio n and Epidemiolog ical Registry (NRER) operates in the country, The gen eral cli- ent ofthe Registry is the Mini stryof Em ergency Situation s. The lead organiza tion is the Medical RadiologicalResearch Cen treoftheRussian Acad- emyof MedicalSciences (RAt\1S) resp onsibl e for sampling primary medical and dosimetric data through24 regionalcentres (2).

The NRERinvolves3 main data bases:the Reg- istrationList of personsexposedto radia tionwhich was established on special dosim etri c criteria ac- cordingtoDecree1948oftheGovernmentofRus- sia; theChernob ylRegistry (since1992theRussian National Medical and Dosimetric Registry - Ri"lMDR); and the Registry ofInterdepartmental ExpertCouncils.

In this article we will enlarge on radiation- related epidemiologicalanalysisof the Chernobyl Registry ofRussia (R.t~MDR).

Current status of the Russian National Medical and Dosimetric Registry

Fig. 1presents information on thegrowth of the number ofregistran tsin theRt"l MDRfrom1986 to 1995.AsFig. 1 shows, during all these yearsofits existence the data baseof the'fede ra llevelofthe Ri"lMDRkeptaccumulating medical dosim e tric in- formation and as of 01.09.95 comprises data on 435 276 peoplefrom throughout theRu ssian Fed- eration.

aAlternative Mem ber ofRussian Acad emy ofTechno logical Sciences, Professor,DeputyDirecto r, Medical Radiological ResearchCentreRAMS(MRRC RAMS),Obninsk,Russia.

bAcad emician of RAMS,Professor, Director, MRRC RAMS, Obninsk,Russia,

22

Fig.1

Increaseinthenumberofregistrantsin theRussian National Medicaland Dosimetric Registry(RNMDR),1986-1 995 Accroissement dunombre d'inscritsau Registre medicalet doslrnetrtque national de Russie,1986-1995

435276

251758 20679126928 174262190050

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

The RNMDR registrants are divided in to 4 groups:

Registr ation group 1 - emergency workers - 152 325 (35.0%);

Registrationgroup 2 - evacuees and the resettled- 12889 (3.0%);

Registration gro up 3 - residents (personsliving or having lived in mo- nitored territori es) 251246 (57.7%);

Registratio n group4 - chi ld ren born to emer- gency workers of 1986- 1987- 18 816 (4.3%). Fig.2demon stratesth edistribution ofperson s registere d in the RNMDR, based on th eirrepresen- tation in regional cen tre s.Theregistryof the Cen- tral Region does not include 4 co ntamin ated oblasts (provinces) - Bryansk, Kalug a, Ore! and Tula - as eachof them hasitsown regiona lcentre.

The maximum numberofpeople registered in Bryansk Oblast (158 182) is determinedbythe to- talpopu latio nlivi n^r in the territory with thehigh- est levels ofrad ioactivecontamination in Russia.

Amongregional centres estab lishedalong territo- rial-administrative divisions of Russia, the maxi- mum numb rofregistrants isin the Nor th-Cau ca- sus R gion (28:-13 Prople) de termined by the nu mb'1'oferne rr ne)'workersliving there.

ex-ar eo mpo ition ofthe contingent regis-

ter-d in th 'MDR isas follows:men - 281775

Rapp.trimest.statist.sanit.mond.,49(1996)

Fig. 2

Regionaldistributionof registrantsin the RussianNationalMedicaland DosimetricRegistry (RNMDR) Repartitionregionaledu nombred'inscritsau Registremedicalet doslrnetrlque national de Russie,1986-1996

435 276 persons - personnes

D

^0-5000

D ^{. . .}

^5000-10000

10000-20 000 20 000-50 000

•

^{>50 000}

1 Northern- Nord 2 Northwest -Nord-Est 3 Central - Centre 4 Volgo-Vyatsky 5 CentralChernozem -

Chernozem central 6 Povolzh

7NorthCaucasus- NordCaucase 8Urals - Ourals 9 WesternSiberia-

Siberie occidentale 10 EasternSiberia-

Siberieorientale 11 FarEast- Extremeest Industrialregions- b Regions industrielles

a

D D

a

Adolescents 3.9%

Children - Enfants 19.2%

RG2 3%

Note:RG=Registration group- Grouped'inscrits, _WHO96443

(64.7%); women - 153 501 (35.3%); chi ldren - 83598 (19.2%); adolescents- 16906 (3.9%); total adults-334772 (76.9%).

Mortality, morbidity and disability among emergency workers: factual data and forecasts

Fig. 3 illustrates the distribution density f(D) of external expo su re doses for emergency workers included in the Rt"lMDR system. As is seen from Fig.3 thedistribution of doses is complicatedand is

ch aracterized by the presence of several peaks (1,5, 10 and 20-25 cGy). This distribution was ob- tained using su pe rposition of distributions of the variousdatesat which each emergencywo rke r be- gan workin g in the radioactive con tam in ation zone.

With regardto th e age distributionofemergen- cy workers (the average age at the time of th e accidentwas 33 years) and dosimetric data,Table1 shows projections of excess mortality from malig-

Table 1

Predicting late effectsof radiation on mortalityfrommalignant neoplas ms among emergencyworkers 20years after the exposu re (Russia,1995)

Tableau 1

Pred iction des effets tardifsdesrayonnements surlarnortalite due

a

des neoplasrnes malins chez leperson nelde secours 20ansapres I'exposition,Russie,1995

Year of Numberof Meanabsorbed Collective dose Excesscancer deaths Natural cancerdeaths- Attributive risk- employmentin the emergency dose(cGy)- (menxGy)-Dose dueto the exposure- Deces par cancer Risque d'attribulion

zone-Annee workers- Dosemoyenne collective(hommes Mortalite cancereuseexcedentalre nature l(%) (%) d'emploidans Nombre absorbee(cGy) xGy) due it I'exposition

lazone d'agents leukaemia- All types- leukaemia - All types - leukaemia - Alltypes-

desecours teucemie Tous types Leucernie Tous types teucemle Tous types

1986 46575 15.9 7405.4 22 84 45 1945 32.8 4.1

1987 48077 8.95 4302.9 11 47 45 1952 19.6 2.4

1988 18208 3.3 600.9 2 7 17 768 10.5 <0.1

1989 5475 3.2 175.2 2 6 234 7.4 <0.1

1986-1989 118335 10.5 12483.1 35 140 113 4899 23.6 2.8

Wld hlthstatist.quart.,49(1996) 23

Fig. 3

Distribution (f(D)) of external exposure doses (D) foremergencyworkersregisteredin the RNMOR

Distribution (f(O)) des doses 0 d'expositionexterne pour lepersonnel d'interventioninscrit au Registremedical et doslrnetnque national de Russie

0.15-,-- - - - -- -- -- -- ---, 0.1 - , - - -- - - -- -..., a. allemergency workers

~

» 0.1

t!)

~

g

0.05

0.075

&

~ 0.05

0.025

b. 1986

@i?0

o

External exposure doses -Doses d'expositlonexterne

o

External exposuredoses- Doses d'expositionexterne

0.3-,-- - - -- - - ---, 0.4..--- - - - - -- - - ,

0.25

c.1987

C§D

_0.3-

d.1988

C1iliD

» 0.2

t!)

~ ^0.15

~

_{~ 0.2-}

o

Externalexposuredoses- Doses d'expositionexterne

o

External exposure doses -Doses d'expositionexterne 0.4..--- - - -- - - - , 0 . 6 . . - - - -- - --'-- - - --,

o

External exposure doses-Doses d'exposition externe

o

External exposure doses- Doses d'expositionexterne

I

f.1990

~

0.5-

» 0.4-

t!)

~

~ 0.3-

::

_0.2-

t ·

0.1- 0 ^i~'\

e.1989 0.3-

C§)

0.2-

0.1-

hi

&

Note:

Rg.3a.Distribution (f(D)) for allemergency workers - Distribution(f(D)) pour"ensemble dupersonnel d'intervention WHO96444 Figs.3b·3f.Distributions (f(D)) fordifferent dates of arrival inthecontaminated areas (1986, 1987, 1988,1989and 1990)areshown separately,with the numberof workers(samplesize)indicatedinsidethe oval. - Les distributions (f(D))pour lesdifferentes dates d'amveedans les territoirescontammes(1986,1987,1988, 1989, 1990)sont montreesif part.avec le nombredepersonnels d'intervention(tailledeI'ochantillon)indique

a

l'interieurde "ovale.

nant neoplasm s am o n g emerge n cy workers 20years after exposure. Excess radiat io n-induced mortality (attributive risk)from all malignantneo- plasms wasfound ^to be 2.8%; the corresponding figureforleukaem ia caseswas23.6%.

Asisevide n t from Table1,thedata on collective an dmean doses of externalradiation areestim ated on the basis of th e informatio n about radi ation

doses received h Ru: ian emerge ncy wor kers re- corded in official do urnentsof theMinistri esand Departme n tswhich se nt them to workin the3D-km zone.

Projc lions of mo r tality from malignant neo- pla: m arc in agr 'rrn e n t with the mortali ty rates ob. rvxl in th - Rl' IDR from these causes for eme rge ncyworkir (Fig.4). Mortali tyofem erge ncy

24 Rapp.ttimest.statist.sanit.mond.,49(1996)

Fig.4

Death rate of emergency workers from malignant neoplasms, 1990-1994

Taux de rnortatite du personnel d'intervention due

a

^des

neoplasmes malins, 1990-1994

Fig. 5

Death rate from all causes for emergency workers in various economic regions of the Russian Federation, 1990-1994 Taux de rnortalite (toutes causes confondues) du personnel d'intervention dans les zones econoruques de la Federation de Russie, 1990-1994

workers from malignant neoplasms does not ex- ceed the control rate. No close dependence of mor- tality from malignant neoplasms is seen here.

Therefore, the relative risk of mortality from malig- nant neoplasms among emergency workers who received doses higher than 25 cGy amountsto lA.

However, the 95% confidence interval of this esti- mate is within the range of 0.61-2.16 (i.e. it in- cludes the value of 1.0) and does not allow one to make a conclusion about dose dependence. It should be noted that in spite of significant growth in the mortality rate from all causes among emer- gency workers in 1990-1994 this index does not exceed the control values (Fig.5). Thus, the health effects on mortality rates (from all causes and ma- lignant neoplasms) actually observed during the 9 years since the CNPP accident are in agreement with forecast estimates.

The more complicated problem relates to the prediction and interpretation of actual data by morbidity and disability rates for emergency workers (3).

Table 2 shows a comparison of morbidity rates per 100 000 people for general classes of diseases, both for the population of Russia as a whole and for emergency workers. Itis clear from Table2 that morbidity rates among emergency workers in a series of cases repeatedly exceeded the analogous ones for the population of Russia. Undeniably, the levels, completeness and quality of prophylactic medical examination of emergency workers differ greatly from the usual Russian practice. In fact, the peculiarity of prophylactic medical examination of emergency workers is that for their examinations the most currently available methods of disease diagnosis are applied, and the work is carried out by trained and competent specialists. Thus, accord- ing to the data of the Medical Radiological Re- search Centre (MRRC) of RAMS the diagnosis of primary registered diseases by specialists at this

100

0 0 0 0 80

0 0 0 0

o~

o~

~:;:,

60

~O ' " Cl.

Cl.",

" , . " ,

- uco,,,,

40

~-o

:5", co-o"'x

Cl:;:,

~ 20

0 1990 1991 1992 1993 1994

2 3 4 5 6 7 8 9 10 11 12 Regions - Regions

1 Russian Federation-Federation de Russie 2 Northern region - Region nord

3 Northwest region - Region nord-ouest 4 Central region - Region ducentre

5 Volgo-Vyatsky region - Region de Volgo-Vyatsky 6 Central Chernozem region - Region centrale-Tchernozem 7 Povolzhsky region - Region de Povolzhsky

8 North Caucasus region - Region duCaucase nord 9 Urals region - Region de l'Oural

10Western Siberia region - Region de la Siberie occidentale 11 Eastern Siberia region - Region de laSiberie orientale 12Far East region - Region deI'extreme Est

• p<0.05; .. p<0.012

institution is several times higher than by local physicians. In this situation it is very difficult to choose an adequate control group for comparison.

It is known that the social and psychological factors connected with the Chernobyl accident are of great importance as causes of pathology and morbidity among emergency workers. In combina- tion with radiation effects, this can be defined as the "Chernobyl syndrome". Attempts to deter- mine the significance of the role of radiation in this complex syndrome are very important. There- fore. morbidity and disability rates were estimated

Wld hlthststist. quert.,49 (1996) 25

Table 2

Prevalence of diseasein the total population of Russia and in emergency workers in 1993 (per 100 000) and ratio of morbidity rates

Tableau 2

Prevalence de la maladie dans la population russe dans son ensemble et parmi le personnel de secours en 1993 (pour 100 000) et ratiodes taux de morbidite

Classes ofdiseases- Classesde maladies Populationof Russia- Populationrusse Emergencyworkers- Ratioof morbidityrates - (rate per100 000) Personneldesecours Ratiodes tauxde morbidite

(rateper100 000)

Neoplasms - Neoplasmes 788 747 0.9

Malignant neoplasms» - Neoplasmesmalins^a 140 233 1.6

Diseases of the endocrine system - Maladies 327 6036 18.4

du systerne endocrinien

Diseases of theblood and blood-forming 94 339 3.6

organs - Maladies du sang et des organes sanguinoformateurs

Mental disorders- Maladies mentales 599 5743 9.6

Diseasesof the circulatory system- 1472 6306 4.3

Maladies du systeme circulatoire

Diseases of the digestive system - 2635 9739 3.7

Maladies du systems digestif

Allclasses of diseases - Toutes classes 50785 75606 1.5

de maladies

aFormalignant neoplasmsthestandardizedindex for age distributionof emergency workers asof1993 is given.- Pour lesneoptasmes malins,ondonneI'indice standardise dela structure parage dupersonnel de secoursen1993.

for the following groups - 0-5 cGy,5-20 cGy,and over-20 cGy- based on dosimetric data for emer- gency workers included in the RNMDR. In this case, the contingents of emergency workers ex- posed in the range of 0-5 cGy were used as an interval control group.Asis seen from Table3,the morbidityratesfor aseries of diseas esin the 5-20

cGyand over-20 cGy dose groups are significantly higher than those in the 0-5 cGy dose group.The over-20 cGy dose group consisted almost entirely (99.1%) of the 1986-1987 emergencyworkers.In the 5-20 cGydose group,the emergency workers of 1986-1987 represent 91.2%. In the lowest-dose group (0-5 cGy) the emergency workers of 1986-

Table3

Diseases among emergency workersin different dose groups in 1993:comparison of morbidityrates per 100 000 persons, Russia,1995

Tableau3

Maladiescontractees par le personnel de secours dansditterents groupes de dose en 1993:comparison des taux de morbidite pour 100 000 personnes,Russie,1995

Classesofdiseases - Classes demaladies Dose groups - Groupes dedose

0-5cGy 5·20cGy >20cGy

Neoplasms - Neoplasrnes 690 648 747

Malignant neoplasms - Neoplasmesmalins 217 232 225

Diseases of the endocrine system - 5270 6120^a 6075^a

Maladiesdu systems endocrinien

Diseases of the bloodand blood-forming organs -

Maladies du sanget des organes sanguinoformateurs 213 354a 450^a

Mental disorders - Maladies mentales 5178 5490 5472

Diseasesof the circulatory system -

Maladiesdu systerne circulatoire 5287 6090a 6648^b

Diseases of the digestive system - Maladies du 9106 9743 9515

systems digestif

All classes of diseases - Toutes classes de maladies 69831 75 346³ 75785^a

• Rates differ significantly(p<0.001fromcorrespondingones inthe0·5cGygroup.-Ladifference enlleleslaux estslgnlficative(P<O,OOI ) parrapport

a

ceux dugroupe dedose 0-5cGy.

b Rates differsignificantly (p<O.001)fromcorresponding onesin the5·20cGydosegroup.-La differenceentre Ies tauxestslgnillcalive(p<O,OOI)parrapport

a

^ceux

ou groupededose 0·5cGy. .

26 Rapp.trimest.statist. sanit.mond.,49 (1996)

Table 4

Changesindisabilityrates per 1000 personsin 1990-1993dose groups(RNMDR data).Russia.1995 Tableau4

Evolutiondestaux d'incapacite pour1000 personnes,selonles groupesdedose en1990-1993 (donnees du Registre medicalet dosimetriquenational de Russie), 1995

Year of observation- Annee d'observation Dosage groups - Groupesde dose

0-5cGy 5-20cGy >20 cGy

1990 6.0 10.3 17.3

1991 12.5 21.4 31.1

1992 28.6 50.1 57.6

1993 43.5 74.0 87.4

198 7 comprise less tha n half the cohort (48.9%) . Then,usin g a sta n dard multifactoria l analysis two com pe ti tive fa ctors we r e examined from the viewpo intof thei r influen ce on mor- bidity rates: (a) dose (with 3 gra da ti o n s of 0-5 cGy,5-20 cGy an d over 20 cGy); an d (b) date of arr ival in the radiati on zone (wit h 3 grada tio ns as well : emerge ncy workers of 198 6 , 198 7 an d 1988-1990). Using the analysis of morbi dity rate s on 3 classe s of diseases (ofth e endo crine syste m, blood and bloo d-for m ing org an s , as wellas mental disord e rs) as an example, itwas esta b lish e d tha t the facto r of the date of arr ival inthe radiation zone (1986, 198 7 ,1988-1990 )is by far the determining one rel ative to the do se facto r an d its influen ce on mo r b id ity. Th is mean s that the he alth status of emergen cy workers- first and forem o st those who worked in 1986 and 198 7- is cause for particular ala rm.

Table 4 pr ese n t'> the disability rates among eme rge n cy workers, as afact o r ofthe external radi- ation doses received .In the seco n d and third dose gr o u ps these ratessigni fica n tly exce e d correspond- ingcoe fficien ts for thefirstdose gro u p (0-5cGy). It sh o u ld be noted that the disabilityratesfor emer- gency worke rsas a whol e are more than 2.8 to 3.2 timestheanalogous con tro lgro u p in Russia.

Thus,for thecoho r tof emerge ncyworke rs reg- iste red in the RNMDR two main conclus io ns may be drawn : (a) fac tua levidence for the period just en ded an d progno stica tio n ofto tal mortality rate as wellasthatfrom malig nan t ne o pl asmsmade on the basisofradiation risk coefficie nts byICRP are in agreeme nt with obse rved rates wh ic h do not exceed co rre spo n d ing con tro lvalues in the Rus- sia nFede ra tio n;an d (b) theeme rgen cy work ers of 1986 and 1987co m p rise a high er-risk gro u p with re gard tomorbidity anddisab ility rates.

Summary

Ten years have elapse d since the Chernoby l acci- dent. Thegravesttechnologicallygenerated acc ident Wld hlthstatist. quart.,49(t996)

throughout human history has attract ed considerable attention fromthewholeworldcommunity. At the same time,the problemofestimating thetotal damage tolife and health ofpeople exposed to rad iationremainsvery complicated (4,5).The negative effects of Chernoby l include a spectrumof factors whic h mayreinforce each other. In partic ular. to date there are no theoretical modelsor practicalrecommendationson estimating the contribut ionof the social,psychological or emotional factors that surround diseases due to radiation acci- dents. On the other hand,for maximumeffectiverehabil- itation of the affected population,theimpartial determi- nation of the contribution by both radiation and non- radiationcomponentsis necessary.Therefore,the con- tinuation of long-stand ing investigations within the frameworkoftheNational Radiation and Epidemiologi- calRegistryalongwithobtaining new scientific datain the field ofradiation epide miology is ofgreat pract ical importancein limiting the health consequencesofthe accident.

R esume

L'accident de Tchernobyl et les risque s de rayonnements: evolution des taux

epidemiologiques (taux de morbidite, d'incapacite et de deces) en tonction ^des

donnees figurant dans le registre national

Dix annees se sont ecoulees depuis I'accident de Tc hernobyl. L'accidenttechnologiquele plus gravede I'histoire de l'hurnanite a attire I'attention de toute la cornrnunaute mondiale auplushaut point. Pourtant,les problemes relatifs

a-

I'estimation de I'ensemble des deqats occasionnes

a-

la vieet

a-

lasante des personnes exposees aux rayonnements demeurent tres compli- ques(4. 5).Les consequencesdesastreusesde Tcher- nobyl comprennent unevariete defacteurs quirisquent de se renforcermutuellement. En particulier,il n'existe

a-

ce jour ni rnod ele theoriquenirecommandationsprati- ques sur I'estimation de la contribution des facteurs sociaux,psychologiques ouaffec tifsauxmaladiesdues

a

^{des accidents} radiologique s. D'autre part, en vue d'une readaptationdes maladesla plus efficace possi- ble,ilimporte de determiner dernaniereobjecti ve Ella fois la contrib utiondes rayonnementsproprementdits 27

et celle des elements autres que les rayonnements. La poursuite d'enquetes de longue durse dans le cadre du registre radiologique et epidernioloqique national et l'ob- tention de nouvelles donnees scientifiques dans le do- maine de l'epidemioloqie des rayonnements reverent par consequent une grande importance sur le plan pratique pour limiter les consequences sanitaires de I'accident.

References/References

1. Ivanov, V.K. et al. Planning of long-term radiation and epidemiological research on the basis of the Russian National Medical Dosimetric Registry. Nagasaki symposium on Chernobyl and. future. Amsterdam, Elsevier. 1994, pp 203-216,

28

2. Ivanov, V.K. etal.Information systems and modelling: data and organizational aspects of the Chemobyl State registry.

Proceeding of the First Conference of International Simulation Societies.Zurich, 1994,pp 579-583.

3. Mould, R.F. et al. Chernobyl update on health and the

"Sarcophagus". Current oncology, 3: 151-162, (1994).

4. TsybA.F. etal.Disease indices of thyroid and their dose dependence in children and adolescents affected as a result of theChernobylaccident. Nagasaki symposium on Chcrnobs!

update and future.Amsterdam, Elsevier, 1994, pp 9-19.

5. Ivanov, V.K. etal.Radiation epidemiology of cancer- and non-cancer thyroid diseases in Russia after the ChNPP accident: prognostication and risk estimate. Radiation and risk, Bulletin of the National Radiation and Epidemiological Registry,special issue 95( 1): 3-29 (1995).

Rapp,

tnmee:

statist, sanit. mood.,49(1996)